Fighting Extinction with Stem Cells

Northern White Rhino
Photo courtesy of the San Diego Zoo

Angalifu and Nola spend their days roaming through a 213-acre habitat modeled on the African savannah. These two-ton white rhinoceros are a couple of the only eight known Northern White Rhinos left on the planet.

Conservation efforts have traditionally focused on protecting habitat and outlawing poaching to save endangered species. Now conservationists are adding a new tool to their repertoire: stem cells.

“These beautiful animals are on the brink,” said Oliver Ryder, the chief geneticist at the San Diego Zoo’s Institute for Conservation Research. “There are a few left, but it’s not clear they’re capable of reproducing.”

Ryder has teamed up with Scripps Research’s Jeanne Loring, a world-renowned stem cell researcher, to try to save the rhinos and other endangered species using some of the same stem cell breakthroughs that might one day treat disorders like Alzheimer’s and Parkinson’s diseases in humans.

The team is using materials from Ryder’s Frozen Zoo, a lab where skin cells and DNA from 12 white rhinos and more than 8,000 other animals are stored at -280F. The Zoo has been collecting cell cultures from exotic animals since the 1970’s, in the hope that someday the cells could be used in some way to rescue endangered species.

This winter, Inbar Friedrich Ben-Nun, a postdoctoral researcher in Loring’s lab, used tissue from the Frozen Zoo to create stem cells from the silver-maned drill, Africa’s most endangered primate. She did it using a new method that reprograms adult cells, causing them to behave like embryonic stem cells, which can form all of the cell types in the body.

In humans, the method could potentially be used to replace damaged tissue or organs. In endangered species, researchers are hoping to use the cells to improve the health of existing animals, and perhaps someday to take it a step further and use them to rescue the waning animal populations by cloning them.

On June 1, the new stem cells morphed into brain cells.

“We were very excited to know that the drill stem cells could generate nerve cells,” Loring said, “but we know that there is still a lot of work to be done.”

The San Diego Zoo has been involved with efforts to clone endangered species in the past. But the older and more common methods of cloning, like those used to clone Dolly the sheep in 1996, are extremely inefficient.

That’s why Loring’s accomplishment is especially exciting.

A few researchers elsewhere have toyed with the idea of resurrecting long-dead animals like the wooly mammoth, but the San Diego group has other priorities.

“We focus on reducing the risk of extinction for species that are here now,” Ryder said. The clock is ticking: Rhinos don’t usually live past 50, and Angalifu is nearing 40.

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